A firefighter typically faces a variety of challenges hindering the firefighter's ability to locate and extinguish a fire. In modern day, interior structure firefighting, the prevalence of synthetic materials in both residential dwellings and commercial occupancies causes fires to burn hotter and faster, to emit thick, black, and often poisonous, smoke that usually obstructs the firefighter's vision, to emit flammable, poisonous gases such as carbon monoxide and hydrogen cyanide, and to generate loud ambient noise or “fireground wind” that usually impedes the firefighter's hearing. The thick, black smoke typically builds up at ceiling level and banks down to the floor, thereby creating a substantially zero-visibility environment. Heavy protective firefighting equipment or bunker gear, such as self-contained breathing apparatus (SCBA), often dulls the firefighter's normal human senses, thereby sometimes causing the firefighter to be less alert to developing hazards, such as “flashover”, which occurs in a compartment fire when the total thermal radiation is sufficiently high such that flammable products of pyrolysis are generated from all exposed combustible surfaces within the compartment. Each flammable gas in the compartment has a flash point, and each flammable gas-air mixture in the compartment ignites at its own auto-ignition temperature when a flame or spark is not present. Once the lowest auto-ignition temperature is reached for a first gas-air mixture, a laddering effect occurs in which the ignition of the first gas-air mixture raises the temperature in the compartment, thereby causing a second gas-air mixture to ignite when its auto-ignition temperature has been reached. The result is a sudden, cascaded, frequently explosive, and sustained, transition from a growing fire to a fully developed fire. Flashover is often fatal to a firefighter remaining in the compartment even for short periods of time. It is, therefore, important for a firefighter to know when temperatures and/or gases in his/her vicinity are approaching conditions leading to a flashover so that the firefighter may take appropriate action, including moving away from the flashover vicinity to a safer location, or cooling the flashover vicinity with water from a hose.
A related hazard is “smoke explosion” in which the temperature reaches a level sufficient to ignite ambient smoke particles, thereby forming an explosive, and usually fatal, fireball. Obstacles, such as furniture, concealed by ambient thick, black smoke, may physically impede the firefighter's progress and cause the firefighter to lose his/her sense of direction, which hampers the firefighter's search for, and extinguishing of, the source of the fire. To avoid such smoke, obstacles, gases, and heat, especially in a zero-visibility environment, firefighters must often crawl upon the floor, thereby making the locating, and the extinguishing, of the source of the fire yet even more difficult and slower.
Stand-alone, handheld thermal imaging cameras are currently used by firefighters to locate the direction and intensity of thermal zones of a fire, and stand-alone, handheld gas detection meters are also currently used to detect flammable gases. As advantageous as such cameras/meters have been as firefighting accessories, the cameras have relatively narrow fields of view, and such cameras/meters are relatively expensive to purchase. Typically, there is only one such camera/meter allocated to each fire truck, and, hence, only one firefighter from the truck, as a practical matter, will benefit from their use. The existing cameras/meters are hand-operated, thereby occupying at least one, if not both, of the firefighter's hands, which might otherwise be more useful in handling other crucial firefighting tools. It is customary for one of the firefighter's hands to be occupied by following a hand lead on a search through a burning structure.
Accordingly, there is a need to display the direction and intensity of thermal zones of a fire, and/or to display hazard warnings, such as conditions leading to a flashover or smoke explosion, to a firefighter on an interface that is readily, rapidly and efficiently comprehensible without distraction or obstruction of the firefighter's vision, and without occupying the firefighter's hands, and whose cost is relatively inexpensive such that a fire department can readily equip each firefighter with his/her own wearable safety apparatus employing said interface, thereby safeguarding all their firefighters' lives and health.
Skilled artisans and practitioners will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.